Over twenty years of research in the field of HIV vaccine have shown that the use of replicating virus to stimulate the immune system is one of our best hopes to develop a vaccine. Recently a cytomegalovirus-based vaccine strategy has successfully protected half of the animals vaccinated. However, this success rate needs to be improved, notably by the use of live viral vectors that restrict HIV replication at the mucosal portal of entry. The capacity of humoral and cellular immune responses in mucosal tissues to block or contain replication at the initial stage of virus transmission may have a profound impact on the ability of a vaccinated host to resist infection. An ideal vaccine should provide a life-lon stimulation of the immune system with viral antigens and should focus the immune response at the site of primary replication of HIV. Recent breakthroughs in vaccine development have used highly immunogenic virus-like particles (VLP) as antigen carriers to stimulate the immune system. This is particularly true for Papillomaviruses (PV). These VLP can also be used to encapsidate either fully infectious PV genome or expression plasmids. These particles are infectious both in cell culture and in vivo. A PV called RhPV has been isolated from a Rhesus macaque giving the opportunity to test PV as SIV antigen vectors. Pseudotyped RhPV has recently been used by our collaborator to successfully inoculate Rhesus macaques giving the possibility to manipulate this virus without losing infectivity. The use of RhPV as a SIV vaccine in macaque followed by SIVmac challenge will be the best model possible to investigate the potential of HPV as an anti-HIV vaccine in humans. However the limiting packaging capacity of RhPV leads us to propose a completely new live vaccine strategy based on mucosal infection with trans-complementing papillomavirus that would still be replicative and would promote antibody production and anti-SIV central memory CD8+ T cells expansion at the oral, rectal and vaginal mucosa for a prolonged period of time. Therefore, specific aims of proposal will be: 1) To design a RhPV vector that leads to long-term expression of SIV antigens in rhesus macaques vaccinated by vaginal, rectal and/or oral routes; 2) To experimentally infect female macaques with this trans-complementing RhPV/SIV vector and investigate the nature of the immune responses induced and safety over 12 months; and, 3) To investigate the protective efficacy of the trans-complementing RHPV/SIV vaccine following intravaginal or intrarectal challenge with multiple low-dose homologous SIV strains challenge. Our work should provide a proof-of-concept in which we will question the capacity of RhPV, as a vaccine vector, to generate strong and long-term anti-SIV immunity at the genital site.